Which is better for golf?

The Flak 2.0 XL. Its Prizm Golf lens is tuned for reading greens, and the semi-rimless frame keeps your view clear when you look down at the ball.

Which has better coverage?

The Flak 2.0 XL has wider coverage at 59 mm per lens. The Sphaera Slash is taller but narrower, so it covers less at the sides.

Which fits a narrow face?

The Sphaera Slash is listed as a narrow universal fit, so it suits smaller faces better. The Flak 2.0 XL is a standard fit and can feel loose on narrow heads.

Is the Sphaera Slash worth stepping up to?

Only if you want the shield look and the 24K mirror. The Flak 2.0 XL offers more lens choices and a proven sport fit.

Do both block UV and resist impact?

Yes. Both use Oakley's O Matter frame and polycarbonate lenses with full UV protection and impact resistance.

Oakley Flak 2.0 XL Prizm Golf vs Oakley Sphaera Slash

Buy the Flak 2.0 XL if you want a proven all-round sport frame with wide coverage, a secure grip and a huge range of lens tints. Buy the Sphaera Slash if you want a bolder, single-lens shield look with a strong 24K mirror and a snug narrow fit. The Flak 2.0 XL has the longer track record and more lens options; the Sphaera Slash is the newer, more fashion-forward shape.

Choose the Flak 2.0 XL if you want a versatile sport frame with wide lens coverage, a secure grip and many tint choices.
Choose the Sphaera Slash if you want a single-lens shield style with a bold 24K mirror and a snug, narrow fit.

Prices

Oakley Flak 2.0 XL Prizm Golf: $109.19 at Jomashop.com (last seen Nov 9)
Oakley Sphaera Slash: $297.00 at Nordstrom (checked today)
Difference: the Oakley Flak 2.0 XL Prizm Golf is $187.81 cheaper than the Oakley Sphaera Slash at the latest prices (Nov 9 and Nov 10)